Degradation of cereal bran polysaccharide-phenolic acid complexes by Aspergillus niger CFR 1105

Abstract

Cereal brans such as wheat and rice are abundant sources for obtaining bioactive phenolic compounds such as ferulic and coumaric acids, in turn these can be bio-transformed into high value flavour compounds such as vanillin. Aspergillus niger CFR 1105, found to induce greater amounts of cell wall degrading enzymes, was inoculated into wheat and rice brans, and grown for 24, 48, 72 and 96 h to understand the degradation pattern of non-starch polysaccharides and phenolic acid complexes. Native wheat bran polysaccharides mainly consisted of arabinose, xylose, galactose, and glucose, in % of 27:39:2:30, with traces of mannose, whereas rice bran consisted of arabinose, xylose, galactose, and glucose in % of 9:27:31:32, respectively. Both the cereal bran arabinoxylans were degraded extensively by A. niger at 96 h, whereas the degradation of 1,3/1,4-β- d-glucans and cellulose was negligible. Bound phenolic acids of rice and wheat brans identified by HPLC were found to be mainly ferulic, coumaric, syringic acids in % of 93.6:6.3:0 (wheat), 34.7:55.8:9.5 (rice) and were drastically degraded/utilized at 96 h. The above results have indicated preferential degradation of arabinoxylans of wheat bran by A. niger, which can be exploited to obtain bioactive compounds such as ferulic acid.